Chances are there’s at least one coffee drinker in your household. In ours it’s my husband and, as I’m an organic grower and gardener, I’m regularly eyeing up his spent coffee grounds.
No matter how small your space, if you’re a plant obsessive like me, it’s worth knowing that you can use this nitrogen-rich organic matter in several ways throughout the garden. It’s also preferable to sending spent grounds to landfill, too; globally, a third of food that’s produced is lost or wasted, making it a big contributor to climate change, releasing 8-10% of all human-caused greenhouse gas emissions as it rots. So, finding ways to cut down what ends up in your rubbish bin is a positive step.
You must observe a few caveats before you start flinging coffee grounds about your plot, but, used correctly, coffee waste can form part of your regime to boost soil and plant health …
Break it down
I am a huge advocate of composting. My compost heap is nurtured perhaps as much as my daughter! It’s an unruly second child that requires constant feeding, but rewards me with untold joy when that sweet-smelling compost is ready. It is truly magical to take your waste and turn it into something full of goodness for your soil and plants. Working with a small space? You can get yourself a wormery instead and experience similar pleasures. I add coffee grounds to both, with great results.
For compost piles, you need to add a mix of green (nitrogen-rich) and brown (carbon-rich) materials to get good results. “Green” being grass cuttings, food scraps, green weeds and leaves, manures and (surprisingly, given that they are actually brown) good old coffee grounds. “Brown” additions include cardboard, paper, egg boxes, woody plant material, woodchip, straw and autumn leaves.
Coffee grounds give the compost a decent helping of nitrogen, adding heat and speeding up the process as microbes in the pile break the grounds down. This is also handy in the winter months when there is less green material available. Just layer the waste coffee in with your other ingredients. The process feels a lot like baking a cake, with equally delicious results for your garden!
For wormeries, in moderation and as part of a balanced diet(!), coffee grounds are a lovely addition and my worms have been feasting on them for more than five years now. You could be forgiven for not knowing what a wormery is, but for anyone gardening on a balcony, rooftop or small urban space, I’d urge you to consider getting one.
Wormeries house composting worms (different from earthworms) that will eat through your fruit and vegetable scraps (and dry matter such as shredded paper and loo-roll tubes) to make beautiful, nutrient-rich worm compost from their castings. This can be used to top-dress pots and garden beds, as well as making a “worm tea” by steeping the compost in water. I don’t dump large quantities of grounds into my worm bin in one hit. Instead I mix with the other ingredients and feed weekly. Our worms are now part of the family and my daughter is intrigued by them.
What to watch out for
As mentioned, coffee grounds are a source of nitrogen – one of the most important nutrients to support plant growth. You will read online that when placed (uncomposted) around plants and used on soil as a mulch, spent grounds can act as a natural fertiliser. And I do know growers who use grounds as a fine mulch. However, proceed with caution, as spent grounds still contain caffeine. Plants that produce caffeine have an allelopathic effect on other plants as a method of survival – this means they can suppress the growth of surrounding species to reduce competition.
So, you must be wary around young plants and seedlings where caffeine can stall growth. If using grounds directly on soil, don’t spread them as a thick layer. I advise mixing grounds with another form of organic matter such as homemade compost, well-rotted manure, green-waste compost or whatever it is you are using to mulch beds or top-dress pots. But if possible, my recommendation would be to compost them first.
There is also a lot of information online about the acidic nature of coffee grounds and the necessity to only place them around acid-loving plants. This may be true of fresh grounds, but studies have shown that spent grounds have a pH that veers towards neutral. It is hard to say without testing each individual batch, but saving the grounds for your acid-loving plants such as blueberries, azaleas, rhododendrons and camellias is unlikely to offer significant benefits. The neutral pH is good news if you want to use the waste coffee more widely in the garden but have been concerned about acidity.
Whenever I get a chance, my favourite early morning routine is to head into the garden with a cup of Nespresso while getting my thoughts for the day in order. Being among my plants has a rejuvenating effect that is hard to find elsewhere. Before I had a garden, my windowsill full of herbs had similar restorative benefits. So pour yourself a cup of coffee, wander outside and get tactile with the plants around you – the buzz you get from your coffee will reach an all-time high!
It’s also worth noting that as well as recycling your spent grounds, you can easily recycle old coffee capsules through Podback, a new industry-wide scheme co-founded by Nespresso, leaving you with zero waste. If you’ve got no more room in your garden for grounds, fear not – Nespresso has its own use for spent grounds, turning them into biogas and soil improver. In east Yorkshire, for example, the compost is being spread on land producing arable crops and cereals.
Anna Greenland is an organic grower who supplies chef Raymond Blanc at Le Manoir aux Quat’ Saisons
Discover what’s next for Nespresso’s journey to carbon-neutral coffee here